1. Field of the Invention
The present invention relates to a numerical controller, and in particular to a numerical controller for controlling relative motions of a tool and a workpiece so that one of the tool and the workpiece is synchronized with a rotating motion of the other.
2. Description of Related Art
There is conventionally known a machine in which one axis of the machine is operated in synchronism with rotation of a cam on another axis so that the motion of the one axis is controlled in accordance with a shape of the cam, as an automatic lathe with a mechanical cam. There have been proposed various devices for performing an operation equivalent to the synchronized operation by the mechanical cam without using the mechanical cam. In these devices, it is common to control positions of axes for a tool in synchronism with a rotational position of a workpiece using ordinary NC data. In these devices, however, since slave axes such as axes for the tool are controlled on the basis of a rotational position of a master axis such as a spindle axis using to a feedback signal of the rotational position of the master axis, it is inevitable that the position controls of the slave axes are delayed with respect to a rotational position of the slave axis especially in variation of rotational velocity of the master axis.
There have been also proposed a device on the basis of time in which time required for moving each axis by a unit amount is controlled so as to control relative positions of the workpiece and the tool, such as disclosed in JP 6-15547A, and a device on the basis of the number of reference pulses in which the respective axes of the workpiece and the tool are controlled to be positioned to be corresponding to the number of reference pulses, such as disclosed in JP 7-271422A. There are difficulties in practicing these methods as described in these publications using the general numerical controllers.